1. Field of the Invention
The present invention relates to a water-spray residual heat removal system for a nuclear power plant, and more particularly, to a residual heat removal system corresponding to a hybrid of a water-spray system and an air cooling system that greatly extends an operating time by spraying a cooling water to a heat exchanger or submerging the heat exchanger in water so that a relatively great amount of heat is removed using a latent heat of water evaporation at an early phase of a nuclear accident at which time a relatively great amount of residual heat is released, and by removing a core residual heat using an air cooling at a late phase of the nuclear accident at which time a supply of cooling water is exhausted or a heat load is significantly decreased.
2. Description of the Related Art
A pressurized water reactor (PWR) may use a steam generator (SG) secondary heat removal system to cool a decay heat. A conventional steam generator (SG) secondary heat removal system may not provide an auxiliary feedwater to a steam generator when a power supply of a water feeding pump is lost, or a water source is depleted due to internal or external causes. When a large disaster such as the Fukushima nuclear accident occurs, it may be difficult to approach an accident site and thus, it may be difficult to separately provide a power source for a cooling system of a nuclear power plant, and it may be difficult to replenish a cooling water to a water tank containing the heat exchanger. In this instance, a core residual heat may not be removed for a relatively long period of time, for example, a period of several days.
That is, a conventional PWR passive auxiliary feedwater system is available to cool a reactor system when a heat exchanger is imbedded with water. Thus, an available cooling time may be limited by a duration of power supplying time and a water volume of cooling tank. When a relatively severe accident occurs in a nuclear power plant due to internal or external circumstances, reproviding a power source or a cooling water may be difficult due to a damaged road or radioactive fallout and thus, a residual heat removal may be stopped, thereby leaving a nuclear reactor susceptible to a critical risk.
Accordingly, a research needs to resolve the issues described above.